Trap-assisted recombination is the dominant recombination mechanism in perovskite solar cells (PSCs) and limits their efficiency. We investigate the attributes of the primary trap-assisted recombination channels and their correlation to defect ions in PSCs. We achieve this by using a validated device model to fit the simulations to the experimental data of efficient vacuum deposited p-i-n and n-i-p CH3NH3PbI3 solar cells including the light intensity dependence of open-circuit voltage and fill factor. We find that despite the presence of traps at interfaces and grain boundaries (GBs), their neutral disposition leads to the high performance of PSCs. And even in the presence of traps at GBs in the perovskite bulk, trap-assisted recombination at interfaces (HTL/perovskite and perovskite/ETL) is the dominant loss mechanism. We find a direct correlation between density of traps, density of mobile defect ions and the degree of hysteresis observed in the current-voltage (J-V) characteristics. Presence of defect states or mobile ions not only limits the device performance but also plays a role in the J-V hysteresis.
It is clear that interfaces (HTL/perovskite and perovskite/ETL) contribute the most to the recombination in PSCs. However, recombination at which interface dominates the operation of the PSC is not straightforward. Most experimental methods to study recombination dynamics are either performed on perovskite thin-films (i.e. not a full device configuration) or done under non-operational conditions (i.e. not under solar fluences), and are often complex. We present an experimental tool to identify the dominant recombination channels in PSCs under operating conditions. We illuminate the cell with red, blue and white light, which gets absorbed differently in the perovskite absorber inducing different charge generation profiles inside the cell. The device characteristics in dark, and under different light sources and illumination intensities discloses not only the dominant recombination mechanism but also its location/position in the device. We confirm this by modelling the operation of the cell and achieve quantitative agreement with all of the experimental dataset.
 T.S. Sherkar et al., Adv. Energy Mater. 2017, 1602432.
 T.S. Sherkar et al., ACS Energy Lett. 2017, 2 (5), 1214–1222.
 T.S. Sherkar et al., (in preparation)