Alanine induced structure reconstruction of PEDOT:PSS films in perovskite solar cells

In the inverted p-i-n perovskite solar cells (PSCs), the widely-used hole transporting layer (HTL) of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) induce degradation problems and hysteresis. To address this issue, several attempts are explored on film formation and interface engineering to improve efficiency. Here, adding alanine into pristine PEDOT:PSS proved beneficial to reconstruct the distribution of the -SO3- and -SO3H groups, resulting an improvement of the charge collection and transport owing to the weakened enrichment of -SO3H. The conductivities of reconstructed PEDOT:PSS films were improved as well as an enhancement of the hydrophobicity. A moderate concentration of alanine could effectively restrain the generation of δ-phase perovskites film and enhance crystallinity of the CsxFA1-xPbI3. The hole trap state of CsxFA1-xPbI3 was slightly reduced to 2.8 × 1015 cm−3. The initial power conversion efficiency (PCE) of 15.48% and stable power output (SPO) of 14.5% were achieved, respectively.