Extended Data Figure 8: Characteristics of solar cells with an ultralow-work-function polymer as the bottom electron-collection contact.
From: Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts
Current density versus voltage for an 80-nm-thick P3HT:PCBM photoactive layer (weight ratio of 1: 0.8) under 100 mW cm−2 illumination (spectral-mismatch corrected) with an ultralow-work-function polymer as the bottom electron-collection contact and PEDT:PSSH as the top hole-collection contact. 20-nm-thick n-doped N1 was deposited as the ECL via spin-coating from DMSO solution onto the ITO layer. The photoactive layer (PAL) was deposited from chlorobenzene. 30-nm-thick PEDT:PSSH was deposited as the HCL via spin-coating from aqueous solution onto the top of the PAL and capped with evaporated Ag. A control cell was fabricated in the same batch by omitting the N1 layer, so that ITO provided the electron-collection contact. The control cell (red) shows poor behaviour with an S-shaped J–V characteristic, whereas the test cell (blue) gives good performance similar to standard cells with evaporated Ca as the electron-collection contact. Open-circuit voltage Voc is given in V; short-circuit current Jsc in mA cm−2, and power conversion efficiency PCE in %. FF, fill factor. Both cells have been corrected for shunt leakage.
