Development Interface Studies and Device Stability Aspects of Inorganic Charge Transport Layers for Organic Inorganic Hybrid Solar Cells

Abstract

Perovskite solar cells (PSC), an emerging photovoltaic technology has achieved an impressive power conversion efficiency (PCE) over 25% (device level lt1 cm2) within a short span of time due to perovskite absorber s intrinsic optoelectronic properties. In PSC, the electron selective layer (ESL) plays a crucial role in efficient electron transport and extraction from the photoactive absorber layer and also minimizes the undesirable charge recombination by suppressing the hole transport, thereby playing a significant role in the improvement of power conversion efficiency and device stability. The most used ESL in PSCs are TiO2, ZnO, SnOx and PCBM and the highest reported PCE is based on TiO2 ESL. Though superior PCE was achieved with TiO2 ESL the need of higher annealing temperature (~450 °C) and the observed instability under UV light results in the degradation of the perovskite absorber over time. The major limitations seen in low temperature processed SnOx thin films are the uncontrolled Vo (oxygen vacancy) and Sni (tin interstitial) defect state formation during the film processing step which leads to higher interface recombination at the perovskite absorber/SnOx interface and poor charge transport from the perovskite layer to the TCO electrode. Keeping this in mind, In the first working chapter, our approach was to employ a simple molecule CsI, in SnOx ESL which helps in achieving both surface and bulk passivation using low temperature (180 °C) solution process technique for the first time newline