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Lead iodide perovskite light-emitting field-effect transistor.

Chin XY, Cortecchia D, Yin J, Bruno A, Soci C - Nat Commun (2015)

Bottom Line: Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-effect transistors.Field-effect carrier mobility is found to increase by almost two orders of magnitude below 200 K, consistent with phonon scattering-limited transport.This demonstration of CH3NH3PbI3 light-emitting field-effect transistors provides intrinsic transport parameters to guide materials and solar cell optimization, and will drive the development of new electro-optic device concepts, such as gated light-emitting diodes and lasers operating at room temperature.

View Article: PubMed Central - PubMed

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.

ABSTRACT
Despite the widespread use of solution-processable hybrid organic-inorganic perovskites in photovoltaic and light-emitting applications, determination of their intrinsic charge transport parameters has been elusive due to the variability of film preparation and history-dependent device performance. Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-effect transistors. Field-effect carrier mobility is found to increase by almost two orders of magnitude below 200 K, consistent with phonon scattering-limited transport. Under balanced ambipolar carrier injection, gate-dependent electroluminescence is also observed from the transistor channel, with spectra revealing the tetragonal to orthorhombic phase transition. This demonstration of CH3NH3PbI3 light-emitting field-effect transistors provides intrinsic transport parameters to guide materials and solar cell optimization, and will drive the development of new electro-optic device concepts, such as gated light-emitting diodes and lasers operating at room temperature.

No MeSH data available.


Related in: MedlinePlus

Experimental and theoretical field-effect mobility and band structures of CH3NH3PbI3.(a) Temperature dependence of field-effect electron and hole mobilities, extracted from the forward sweeping of transfer characteristics at Vds=20 V and Vds=−20 V, respectively. (b) Calculated temperature dependence hole (red curves) and electron (black curves) mobility in tetragonal (T=300 to 160 K) and orthorhombic (T=160 to 77 K) phases of CH3NH3PbI3. The crystal unit cells of the two phases are shown as insets. (c, d) Band structures of the tetragonal (c) and orthorhombic (d) phases obtained by DFT-Perdew–Burke–Ernzerhof method with (solid curves) and without (dotted curves; W/o) spin-orbital coupling (SOC).
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f3: Experimental and theoretical field-effect mobility and band structures of CH3NH3PbI3.(a) Temperature dependence of field-effect electron and hole mobilities, extracted from the forward sweeping of transfer characteristics at Vds=20 V and Vds=−20 V, respectively. (b) Calculated temperature dependence hole (red curves) and electron (black curves) mobility in tetragonal (T=300 to 160 K) and orthorhombic (T=160 to 77 K) phases of CH3NH3PbI3. The crystal unit cells of the two phases are shown as insets. (c, d) Band structures of the tetragonal (c) and orthorhombic (d) phases obtained by DFT-Perdew–Burke–Ernzerhof method with (solid curves) and without (dotted curves; W/o) spin-orbital coupling (SOC).

Mentions: Temperature-dependent electron and hole mobilities were extracted from the forward sweeping of transfer characteristics at Vds=20 V and Vds=−20 V using the standard transistor equation at linear regime47. The resulting values are shown in Fig. 3a. Note that mobilities were not extracted from backward sweeping curves to avoid misleading results due to the large hysteresis. Also, mobilities at higher Vds (that is, in the saturation regime) were not extracted due to the difficulty to identify linear and saturation regimes at all investigated temperatures. A statistical analysis of the distribution of mobility values extracted from independent measurements across four different devices is shown in Supplementary Fig 4. Although some variability in the absolute values of electron and hole mobilities is observed from device to device, their relative magnitude and temperature dependence show consistent trends. From Fig. 3a, both electron and hole mobilities increase by a factor of ∼100 from room temperature to 198 K. Below 198 K, there is no further improvement of electron mobility, whereas hole mobility shows an additional tenfold increase. We attribute the improvement of mobility at low temperature to the removal of screening effects arising from the ionic transport of methylammonium cations. The phonon energy of methylammonium cation was estimated to be ∼14.7 meV from previous combination of density function theory (DFT) and Raman studies48. The observation of weak improvement of field-effect mobilities below 198 K (Ethermal=16.7 meV) is therefore consistent with the quenching of phonon interactions related to the organic cations. This is also in agreement with the weakening of field-switchable photovoltaic effects at low temperature33, strongly suggesting that field-effect transport is phonon limited at room temperature. Despite the remarkable improvement of field-effect mobilities, hysteresis was not completely removed at the lowest temperature investigated. This could be due to the untreated semiconductor–dielectric interface, which is known to affect semiconductor film morphology, number of trap states and surface dipoles, similar to the case of organic FET devices47. The reduction of trap density in single crystal3031 and large grain size thin films32 enormously enhances stability of photovoltaic devices. Thus, improvement of bulk crystallinity is also expected to reduce hysteresis of FETs, with proper control of the morphology of the semiconductor–dielectric interface, where the nanometre thin field-effect transport channel is created47. Both hole and electron mobilities extracted in the linear regime at 78 K are slightly smaller than the corresponding saturation regime mobilities (μe,linear/μe,saturation=6.7 × 10−2/7.2 × 10−2 cm2 V−1 s−1 and μh,linear/μh,saturation=6.6 × 10−3/2.1 × 10−2 cm2 V−1 s−1, extracted at Vds=± 20 V for linear regime and Vds=±80 V for saturation regime from Fig. 2a). A previous study of spin-coated hybrid perovskite channels indicated linear regime mobility values 1 to 2 orders of magnitude lower than in the saturation regime39. The suppression of the linear regime mobility is presumably associated to grain-boundary effects, which give rise to a large concentration of traps. Thus, our reported linear regime mobilities set a lower limit for electron and hole mobilities of CH3NH3PbI3.


Lead iodide perovskite light-emitting field-effect transistor.

Chin XY, Cortecchia D, Yin J, Bruno A, Soci C - Nat Commun (2015)

Experimental and theoretical field-effect mobility and band structures of CH3NH3PbI3.(a) Temperature dependence of field-effect electron and hole mobilities, extracted from the forward sweeping of transfer characteristics at Vds=20 V and Vds=−20 V, respectively. (b) Calculated temperature dependence hole (red curves) and electron (black curves) mobility in tetragonal (T=300 to 160 K) and orthorhombic (T=160 to 77 K) phases of CH3NH3PbI3. The crystal unit cells of the two phases are shown as insets. (c, d) Band structures of the tetragonal (c) and orthorhombic (d) phases obtained by DFT-Perdew–Burke–Ernzerhof method with (solid curves) and without (dotted curves; W/o) spin-orbital coupling (SOC).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491174&req=5

f3: Experimental and theoretical field-effect mobility and band structures of CH3NH3PbI3.(a) Temperature dependence of field-effect electron and hole mobilities, extracted from the forward sweeping of transfer characteristics at Vds=20 V and Vds=−20 V, respectively. (b) Calculated temperature dependence hole (red curves) and electron (black curves) mobility in tetragonal (T=300 to 160 K) and orthorhombic (T=160 to 77 K) phases of CH3NH3PbI3. The crystal unit cells of the two phases are shown as insets. (c, d) Band structures of the tetragonal (c) and orthorhombic (d) phases obtained by DFT-Perdew–Burke–Ernzerhof method with (solid curves) and without (dotted curves; W/o) spin-orbital coupling (SOC).
Mentions: Temperature-dependent electron and hole mobilities were extracted from the forward sweeping of transfer characteristics at Vds=20 V and Vds=−20 V using the standard transistor equation at linear regime47. The resulting values are shown in Fig. 3a. Note that mobilities were not extracted from backward sweeping curves to avoid misleading results due to the large hysteresis. Also, mobilities at higher Vds (that is, in the saturation regime) were not extracted due to the difficulty to identify linear and saturation regimes at all investigated temperatures. A statistical analysis of the distribution of mobility values extracted from independent measurements across four different devices is shown in Supplementary Fig 4. Although some variability in the absolute values of electron and hole mobilities is observed from device to device, their relative magnitude and temperature dependence show consistent trends. From Fig. 3a, both electron and hole mobilities increase by a factor of ∼100 from room temperature to 198 K. Below 198 K, there is no further improvement of electron mobility, whereas hole mobility shows an additional tenfold increase. We attribute the improvement of mobility at low temperature to the removal of screening effects arising from the ionic transport of methylammonium cations. The phonon energy of methylammonium cation was estimated to be ∼14.7 meV from previous combination of density function theory (DFT) and Raman studies48. The observation of weak improvement of field-effect mobilities below 198 K (Ethermal=16.7 meV) is therefore consistent with the quenching of phonon interactions related to the organic cations. This is also in agreement with the weakening of field-switchable photovoltaic effects at low temperature33, strongly suggesting that field-effect transport is phonon limited at room temperature. Despite the remarkable improvement of field-effect mobilities, hysteresis was not completely removed at the lowest temperature investigated. This could be due to the untreated semiconductor–dielectric interface, which is known to affect semiconductor film morphology, number of trap states and surface dipoles, similar to the case of organic FET devices47. The reduction of trap density in single crystal3031 and large grain size thin films32 enormously enhances stability of photovoltaic devices. Thus, improvement of bulk crystallinity is also expected to reduce hysteresis of FETs, with proper control of the morphology of the semiconductor–dielectric interface, where the nanometre thin field-effect transport channel is created47. Both hole and electron mobilities extracted in the linear regime at 78 K are slightly smaller than the corresponding saturation regime mobilities (μe,linear/μe,saturation=6.7 × 10−2/7.2 × 10−2 cm2 V−1 s−1 and μh,linear/μh,saturation=6.6 × 10−3/2.1 × 10−2 cm2 V−1 s−1, extracted at Vds=± 20 V for linear regime and Vds=±80 V for saturation regime from Fig. 2a). A previous study of spin-coated hybrid perovskite channels indicated linear regime mobility values 1 to 2 orders of magnitude lower than in the saturation regime39. The suppression of the linear regime mobility is presumably associated to grain-boundary effects, which give rise to a large concentration of traps. Thus, our reported linear regime mobilities set a lower limit for electron and hole mobilities of CH3NH3PbI3.

Bottom Line: Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-effect transistors.Field-effect carrier mobility is found to increase by almost two orders of magnitude below 200 K, consistent with phonon scattering-limited transport.This demonstration of CH3NH3PbI3 light-emitting field-effect transistors provides intrinsic transport parameters to guide materials and solar cell optimization, and will drive the development of new electro-optic device concepts, such as gated light-emitting diodes and lasers operating at room temperature.

View Article: PubMed Central - PubMed

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.

ABSTRACT
Despite the widespread use of solution-processable hybrid organic-inorganic perovskites in photovoltaic and light-emitting applications, determination of their intrinsic charge transport parameters has been elusive due to the variability of film preparation and history-dependent device performance. Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-effect transistors. Field-effect carrier mobility is found to increase by almost two orders of magnitude below 200 K, consistent with phonon scattering-limited transport. Under balanced ambipolar carrier injection, gate-dependent electroluminescence is also observed from the transistor channel, with spectra revealing the tetragonal to orthorhombic phase transition. This demonstration of CH3NH3PbI3 light-emitting field-effect transistors provides intrinsic transport parameters to guide materials and solar cell optimization, and will drive the development of new electro-optic device concepts, such as gated light-emitting diodes and lasers operating at room temperature.

No MeSH data available.


Related in: MedlinePlus