In one aspect of the present invention, a photovoltaic device is provided. The photovoltaic device includes a window layer and an absorber layer disposed on the window layer, wherein the absorber layer includes a first region and a second region, the first region disposed adjacent to the window layer. The absorber layer further includes a first additive and a second additive, wherein a concentration of the first additive in the first region is greater than a concentration of the first additive in the second region, and wherein a concentration of the second additive in the second region is greater than a concentration of the second additive in the first region. Method of making a photovoltaic device is also provided.

Photovoltaic devices having transparent contact layers are described herein.

A homogeneous optoelectronic reservoir computing system based on a nitrogen-doped GeSbTe material includes an optoelectronic reservoir layer and a readout layer connected to each other; the optoelectronic reservoir layer includes multiple optical synaptic devices based on nitrogen-doped GeSbTe material, and the optical synaptic devices realize perception and nonlinear response of image light signals based on the photoconductive effect of a single light pulse and the paired-pulse facilitation effect under a double light pulse; the readout layer includes multiple electrical synaptic devices based on the nitrogen-doped GeSbTe material, and the electrical synaptic devices realize linear response and image recognition of output signals of the optoelectronic reservoir layer based on linearity, symmetry long-term potentiation function, and long-term depression function. In the system of the disclosure, both the reservoir layer and the readout layer use devices based on the same material.

Photovoltaic devices having transparent contact layers are described herein.

A quantum dot includes: a core including a first semiconductor nanocrystal, and a shell disposed on the core, the shell including a second semiconductor nanocrystal and a dopant, wherein the first semiconductor nanocrystal includes a Group III-V compound, the second semiconductor nanocrystal includes zinc (Zn), sulfur (S), and selenium, and the dopant includes lithium, a Group 2A metal having an effective ionic radius less than an effective ionic radius of Zn.sup.2+, a Group 3A element having an effective ionic radius less than an effective ionic radius of Zn.sup.2+, or a combination thereof. Also a method of producing the quantum dot, and a composite, and an electronic device including the quantum dot.