Progress of new carbon material research in perovskite solar cells

Abstract

A photoelectric conversion efficiency of 3.8% was achieved based on organic-inorganic hybrid perovskites CH3NH3PbBr3 and CH3NH3PbI3 in 2009, and their efficiencies have leaped to 20.1% in the past five years, which are comparable to Cu(In,Ga) Se2 solar cells. The researchers mainly focused on appropriate materials and device structures, high-quality film depositions, careful interface designs and controllable carrier properties. Even so, it is still a long-term work to develop the low-priced, stable, environmental-friendly and highly-efficient perovskite solar cells, for example, the hole transport material spiro-OMeTAD is complicated and expensive, the electron transport material TiO2 must be processed by high temperature annealing and the Au electrode is extensively used, all of which are not conducible to the commercialized application. On this occasion, new carbon materials, such as graphene oxide, carbon nanotubes, fullerene, graphdiyne, etc. have become another highlight of perovskite solar cells due to their excellent thermal, mechanical, electrical and optical performances. Carbon materials are low-cost and highly available industrial materials, which have been applied to highly efficient counter electrodes for dye-sensitized solar cell and quantum dot-sensitized solar cells. The approximate 5.0 eV work function makes carbon material the ideal counter electrode material for perovskite solar cell. Carbon material is endowed with remarkably high charge mobility and electronic conductivity, which has been identified as one of the strongest materials for electron transport in perovskite solar cell. Similarly, a perovskite solar cell using hole transport materials incorporating carbon material shows an improved power conversion efficiency due to enhanced electrical conductivity and carrier mobility because the low electrical conductivity of hole transport material such as spiro-OMeTAD is considered to be an impediment to further enhancement of the power conversion efficiency and a hole transport material with higher conductivity should reduce the series resistance and increase the fill factor, thereby enhancing the power conversion efficiency of perovskite solar cell. In this paper, the research progress of new carbon materials for counter electrode, electron transport materials, hole transport materials in perovskite solar cells are summarized. The power efficiency of perovskite solar cell is enhanced greatly because of the introduction of new carbon materials, which provides a new idea for the further application of new carbon materials and device design of perovskite solar cells.