AN APPROACH TO THE OPTIMAL-DESIGN OF P-N HETEROJUNCTION SOLAR-CELLS USING THIN-FILM ORGANIC SEMICONDUCTORS

In recent work with p-n heterojunction solar cells constructed with pairs of photoconductive organic dyes, we have obtained short-circuit current yields of over 19%. The best results to date have been obtained with the pair chloroaluminum phthalocyanine (ClAlPc) and the bis-methylimide of perylenetetracarboxylic acid (DMP). The preferred configuration is SnO//2/DMP/ClAlPc/Ag. This configuration has the advantage of placing the shorter wavelength absorber DMP against the transparent SnO//2 input surface and facilitating Forster radiationless energy transfer from the DMP phase to the region of the active DMP/ClAlPc junction. It also makes best use of the electron-accepting and electron-donating properties of the two dyes. Through tests of single-dye Schottky cells with a variety of metal electrodes, we have learned that the Fermi levels of these two dyes lie too close together for optimum cell performance. Synthetic variants of the simple perylene dye and of ClAlPc have been prepared for stronger electron-accepting and electron-donating properties, respectively.