High efficiency hybrid PEDOT:PSS/nanostructured silicon Schottky junction solar cells by doping-free rear contact

Abstract

A high doping technique has been widely used for record-efficiency crystalline silicon (Si) solar cells to minimize the series resistance losses and to form a back surface field. However, it requires high temperatures (up to 1000 °C) and involves toxic gases, which may not be compatible for hybrid organic–silicon solar cells. Here, we report that a high power conversion efficiency (PCE) of 13.7% with a device area of 0.8 cm² has been achieved for organic-nanostructured Si hybrid solar cells by inserting a cesium carbonate (Cs₂CO₃) layer between Si and the rear electrode aluminium (Al), which is realized by a solution process under low-temperature annealing (<150 °C). Transient and constant current–voltage, capacitance–voltage, and scanning Kelvin probe microscope measurements are used to characterize the effect of the Cs₂CO₃ layer on the device performance. The insertion of Cs₂CO₃ not only decreased the contact resistance, but also generated a built-in electric field on the rear electrode. The recombination rates are suppressed at the back surface due to the deflection of minority carriers. These findings show a promising strategy to achieve high performance organic–silicon solar cells with a simple, low temperature and cost effective process.