We demonstrate high open circuit voltage photovoltaic cells achieved by reducing the electron leakage current through the introduction of both organic and inorganic electron blocking layers between the donor layer and the anode contact. As an example, the blocking layers reduce the dark current in tin ͑II͒ phthalocyanine ͑SnPc͒ / C 60 solar cells with response across the visible and near infrared spectral region up to a wavelength of 1000 nm, is decreased by two orders of magnitude compared to cells lacking the layers, resulting in a doubling of the open circuit voltage. The structure: indium tin oxide/electron blocker/SnPc ͑100 Å͒ / C 60 ͑400 Å͒/bathocuproine ͑100 Å͒ / Al, has a power conversion efficiency of ͑2.1Ϯ 0.1͒% at 1 sun, standard AM1.5G solar illumination. This work demonstrates the importance of reducing dark current to achieve high organic thin film photovoltaic cell efficiencies.

We describe a hybrid planar-mixed heterojunction (PM-HJ) organic photovoltaic cell based on tetraphenyldibenzoperiflanthene (DBP) and C 70 with a power conversion efficiency of up to 6.4% 6 0.3%. Optimized cells consist of a DBP:C 70 mixed layer at a volume ratio of 1:8 and a 9-nm thick C 70 cap layer. The external quantum efficiency (EQE) in the visible of the PM-HJ cell is up to 10% larger than the mixed-HJ cell that lacks a C 70 acceptor cap layer. The improvement in EQE is attributed to reduced exciton quenching at the MoO 3 anode buffer layer surface. This leads to an internal quantum efficiency >90% between the wavelengths of k ¼ 450 nm and 550 nm, suggesting efficient exciton dissociation and carrier extraction in the PM-HJ cell. The power conversion efficiency under simulated AM 1.5G, 1 sun irradiation increases from 5.7% 6 0.2% for the mixed-HJ cell to 6.4% 6 0.3% for the PM-HJ cell, with a short-current density of 12.3 6 0.3 mA/cm 2 , open circuit voltage of 0.91 6 0.01 V, and fill factor of 0.56 6 0.01. V C 2013 American Institute of Physics. [http://dx.

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We demonstrate the concentration dependence of C60 absorption in solid solutions of C60 and bathocuprione (BCP), revealing a nonlinear decrease of the C60 charge transfer (CT) state absorption. These blends are utilized to study the photocurrent contribution of the CT in bilayer organic photovoltaics (OPVs); 1:1 blends produce 40% less photocurrent. As exciton blocking electron transporting layers, the blends achieve power conversion efficiencies of 5.3%, an increase of 10% compared to conventional buffers.