Photo-Induced Charge Recombination Kinetics in MAPbI 3-

Transcription

1 Electronic Supplementary Material (ESI) for ChemComm. This journal is The Royal Society of Chemistry 2014 Photo-Induced Charge Recombination Kinetics in MAPbI 3- xcl x Perovskite-like Solar Cells Using Low Band-Gap Polymers as Hole Conductors. Jose Manuel Marin-Beloqui, a Javier Pérez Hernández, a Emilio Palomares* a,b a Institute of Chemical Research of Catalonia (ICIQ), Avda. Paisos Catalans 16, Tarragona 43007, Spain b Catalan Institution for Research and Advanced Studies (ICREA), Avda. Lluís Companys, Barcelona E-08010, Spain To whom the correspondence must be addressed: epalomares@iciq.es Page 1 of 6 ESI

2 Scheme S1. Schematic representation of a double heterojunction solar cell. Double because on one side we will use TiO 2 as selective contact for electrons and on the other side, we will use a HTM as selective contact for holes. The difference between the quasi-fermi levels gives rise to the device Voc. Page 2 of 6 ESI

3 Figure S1. Photocurrent vs voltage curves measured before (solid black line) and after (dashed red line) the L-TAS and the TPV measurements under standard sunsimulated solar conditions (100mW/cm AM G). Page 3 of 6 ESI

4 Figure S2. a) Photoluminiscence emission spectrum (λ ex =470 nm) of the different films used deposited onto a glass film following the same procedure for the device fabrication. Comparison between the photoluminescence decay (λ ex =470 nm and λ pr =780 nm) of the raw perovskite film (dashed line) and the one with perovskite/htm (solid line) being the HTMs b)spiro-ometad, c)ptb7 and d)ptb1. From the integrals of these decays was possible to obtain the percentage of the regeneration of the perovskite with these HTMs. These regeneration percentages were 100% for OMeTAD, 96% for PTB1 and 98% for PTB7. All these measurements were carried out under ambient conditions. Page 4 of 6 ESI

5 Device Fabrication The FTO (Fluorine doped Tin Oxide) coated glasses (resistance= 8Ω/cm 2 ) were etched using Zn powder (Alfa Aesar 98%) and a 2 M solution of HCl according to the desired pattern. Afterwards, the substrates were cleaned for 15 minutes in an ultrasound bath with de-ionized water with Hellmax soap, with de-ionized water and finally with ethanol. The substrates were dried and an UV/Ozone treatment was performed for 20 minutes. A 0.65 ml of Ti (IV) isopropoxide (Sigma Aldrich 97%) and 0.38 ml of Acetylacetone (Sigma Aldrich) were mixed in 5 ml of Ethanol. This solution was spun-casted at 3000 rpm for 60s over the FTO. Substrates were calcined at 500ºC for 30 min to obtain the Titanium oxide dense layer. Afterwards, titanium oxide-coated substrates were immersed in a 40 mm TiCl 4 solution at 70ºC for 30 minutes. Then, substrates were cleaned with water and ethanol and heated at 390ºC for 20 minutes. A mixture of TiO 2 paste (18 NR-T Dyesol) and ethanol 2:7 (w:w) was spincoated at 5000 rpm for 30 seconds. The substrates were heated at 325ºC for 30 min, 375ºC for 5 min, 450ºC for 15 min and 500ºC for 30 min. The substrates were heated at 500 ºC for minutes prior to their use. The methylammonium iodide was synthesized as described previously [1]. For the perovskite deposition, a 3:1 molar ratio solution of methylammonium iodide and PbCl 2 (Sigma Aldrich 98%) in DMF was prepared [2]. Perovskite precursor was deposited by spin-coating over the mp-tio 2 layer at 2000 rpm for 1 min. The asdeposited substrates were heated at 120ºC for 30 minutes, and their colour changed from yellow to black. The PTB7 and the PTB1 (1-Material) semiconductor polymers were dissolved in chlorobenzene to obtain a 10 mg/ml solution. The spiro-ometad (Merck) was dissolved also in chlorobenzene to reach a 70 mg/ml. The HTM layer was deposited by spin-coating the solution onto the perovskite at 2000 rpm for 1 minute. Finally, 80 nm of gold metal was evaporated as the anode by thermal evaporation at a pressure not higher than 1x10-6 mbar. All the steps for the perovskite and the HTM deposition were carried out inside the glove box to avoid humidity ([O2] < 100 ppm and [H2O] < 0.1 ppm). Reference. 1 J-H. Im, C-R. Lee, J-W. Lee, S-W Park, N-G Park, Nanoscale, 2011, 3, J. M. Ball, M. M. Lee, A. Hey, H. J. Snaith, Energy &Enviromental Science, 2013, 6, Page 5 of 6 ESI

6 I-V Curves The current-voltage measurements were carried out with an Abet Sun 2000 solar simulator (100 mw/cm 2, AM 1.5 G), calibrated with a silicon photodiode (NREL), attached to a Keithley 2400 digital source meter to apply the voltage and to measure the current. Transient Photo-voltage The transient photovoltage (TPV) measurements were performed using an array of LEDs to simulate the solar light and to increase in controlled manner the cell photovoltage (so called light bias). The small perturbation in the device photovoltage was done with a nanosecond PTI GL-3300 Nitrogen laser (devices were excited at 600 nm). The device was directly connected to a Yokogawa DLM2052 oscilloscope with a high resistance (1MΩ) terminal to obtain open-circuit conditions while the cell was illuminated to obtain the desired photovoltage. When the desired Voc is reached, the laser created the small perturbation ( ΔV), to obtain a monoexponential voltage decay that was registered by the oscilloscope. Laser-Transient Absorption Spectroscopy system The L-TAS measurements were carried out by a pump probe system composed by a Nd:YAG laser system with an optical parametric oscillator (OPO), integrated by an Opolette (HR 255 LD model). The light probe is selected by two Visible-IR motorized monochromators from Dongwoo Optron (DM500i model) placed before and after the sample holder. The detection part consists on an InGaAs photodiode signal enhanced by an AC-coupled home made trans-impedance amplifier. For the data acquisition system a FPGA based data logger was developed in collaboration with RAMDSP ( which allows capturing up to 300ms transients in one laser shot. The time resolution of the entire transient is 2.5 nanoseconds at 14 bits. All the system is controlled by our home-build L-TAS software. Time-Correlated Single Photon Counting Time-Correlated Single Photon Counting (TCSPC) measurements were carried out on an Edinburgh Instruments LifeSpec-II spectrometer equipped with the appropiated PMT detector, double subtractive monochromator and a set of picosecond pulsed diode lasers sources. Page 6 of 6 ESI