Open circuit voltage enhancement due to reduced dark current in small molecule photovoltaic cells

Abstract

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.

Efficient and bright organic light-emitting diodes on single-layer graphene electrodes

“…Although OA-doped graphene has an enhanced work function of B5.1 eV, it is not sufficient for direct hole injection into host materials such as 4,4 0 -bis(carbazol-9-yl)biphenyl (CBP), which has a HOMO level of 6.1 eV. Here we use anode interface layers consisting of the transition metal oxide to further enhance the work function of the graphene anode, similar to their roles of modifying the work function of ITO electrodes in organic electronics [38][39][40][41][42][43] . Note that metal oxides do not grow as uniform films on graphene due to the lack of nucleation to initialize the film growth 44,45 .…”

Effect of leakage current and shunt resistance on the light intensity dependence of organic solar cells

“…Such large variation in the leakage current of organic solar cells is not uncommon and is known to be affected by substrate cleaning procedures, film thickness, electrode interlayers, and film deposition techniques. 5,9,10 In the case of the devices here, the range in R sh is most likely a consequence of spin coating from a hot solution which led to variations in film thickness and film density which in turn affects the degree of cathode diffusion into the active layer.…”

Modified structure of two-dimensional polythiophene derivatives by incorporating electron-deficient units into terthiophene-vinylene conjugated side chains and the polymer backbone: synthesis, optoelectronic and self-assembly properties, and photovoltaic application

“…The non-linear trend is decided by a couple of other factors besides the HOMO levels of the polymers, such as the dark current, blend morphology of the photoactive layers, and interface resistance. 30,34,[53][54][55] The morphology of photoactive layer plays a decisive role in determining the photovoltaic characteristics of PSC devices. [56][57][58] Herein, atomic force microscopy (AFM) was used to investigate the morphologies of the spin-coated lms of polymers/PC 61 BM on top of ITO/PEDOT:PSS, which were prepared by using the same procedure and parameters for preparing the photoactive layers.…”