On the Importance of Morphology Control for Printable Solar Cells

Abstract

Polymer and hybrid solar cells have the potential to become the leading technology of the twenty-first century to convert sunlight to electrical energy because they can be easily processed from solution printing devices in a roll-to-roll fashion with high speed and low-cost. The performance of such devices critically depends on the nanoscale organization of the photoactive layer, which is composed of at least two functional materials, the electron donor and the electron acceptor forming a bulk-heterojunction; however, control of its volume morphology still is a challenge. The main requirements for the morphology of efficient photoactive layers are nanoscale phase separation for a large donor/acceptor interface area and hence efficient exciton dissociation, short and continuous percolation pathways of both components leading through the layer thickness to the corresponding electrodes for efficient charge transport and collection, and high crystallinity of both donor and acceptor materials for high charge mobility. In this chapter we review recent progress of our understanding on how the efficiency of a bulk-heterojunction printable solar cell largely depends on the local nanoscale volume organization of the photoactive layer.