Recent advancement in metal cathode and hole-conductor-free perovskite solar cells for low-cost and high stability: A route towards commercialization

Recent developments in organic-inorganic halide perovskite solar cells created a sudden buzz in renewable energy community. Within a short span of time, the efficiency of perovskite solar cells (PSCs) soared from 2.1% (2006) to 22.1% (2017) by varying each component and device configuration. Recent works have been concentrated on the potential of PSCs to emerge as an economical technology. Elimination of hole transport material (HTM) and metal counter electrode in PSCs can overcome high cost and stability issues. In this review, we outline the recent research progress on the metal cathode and HTM-free PSCs, which is a prospective solution to meet the growing energy demands. Carbon materials are used as an alternative to the conventional metal cathode since, carbon materials possess unique qualities such as low cost, high stability, good conductivity and inherent water resistance. Introduction and discussions of this article include the evolution of PSCs, cost, device architectures, deposition techniques, the thickness of the spacer, morphology of counter electrode and stability.