Device structures, apparatuses, and methods are disclosed for photovoltaic cells that may be a single-junction or multijunction solar cells, with at least a first layer comprising a group-IV semiconductor in which part of the cell comprises a second layer comprising a III-V semiconductor or group-IV semiconductor having a different composition than the group-IV semiconductor of the first layer, such that a heterostructure is formed between the first and second layers.

Provided is a conductive material that is capable of achieving a high-electric conductivity, long-term stability under an atmospheric environment, heat and high humidity stabilities, as well as a conductive film and a solar cell using the same. The conductive material includes a mixture of carbon nanotubes (CNTs) and polystyrene sulfonic acid (PSS acid). The element ratio (S/C ratio) of sulfur (S) to carbon (C) in the mixture may be from 0.001 to 0.1 in terms of the number of atoms. CNTs and PSS acid may make up a content percentage of 10 wt % or more in the mixture. These conductive films comprised of the conductive material 6 may have a weight per unit area of the CNTs in the range from 1 mg/m.sup.2 to 10000 mg/m.sup.2. The solar cell may include the conductive film 7, wherein the film is on the surface of a semiconductor.

A tandem solar cell includes a perovskite solar cell including a perovskite absorption layer, a silicon solar cell placed under the perovskite solar cell, a junction layer placed between the perovskite solar cell and the silicon solar cell, an upper electrode placed on the perovskite solar cell, and a lower electrode placed under the silicon solar cell.

An optical semiconductor element includes an optical receiver including a first semiconductor layer, a heater for heating the first semiconductor layer; and a monitor. A first semiconductor layer that absorbs light and generates electric carriers; a heater for heating the first semiconductor layer; and a monitor including a second semiconductor layer in which dark current is changed by heat generated by the heater.

An optical semiconductor element includes an optical receiver including a first semiconductor layer, a heater for heating the first semiconductor layer; and a monitor. A first semiconductor layer that absorbs light and generates electric carriers; a heater for heating the first semiconductor layer; and a monitor including a second semiconductor layer in which dark current is changed by heat generated by the heater.

The disclosure provides a passivated contact structure and a solar cell including the same, a cell assembly and a photovoltaic system. The passivated contact structure includes a first passivated contact region on a silicon substrate and a second passivated contact region on the first passivated contact region. The second passivated contact region has an opening connecting a conductive layer to the first passivated contact region. The first passivated contact region includes a first doped layer, a first passivation layer and a second doped layer. The second passivated contact region includes a second passivation layer and a third doped layer. The first passivation layer is a porous structure inlaid with the first doped layer and/or the second doped layer in a hole region. Utilizing the passivated contact structure provided in this invention, mitigates the serious recombination caused by metal directly contacting with silicon substrate.

A tandem photovoltaic device includes a silicon photovoltaic cell having a silicon layer, a perovskite photovoltaic cell having a perovskite layer, and an intermediate layer between a rear side of the perovskite photovoltaic cell and a front (sunward) side of the silicon photovoltaic cell. The front side of the silicon layer has a textured surface, with a peak-to-valley height of structures in the textured surface of less than 1 μm or less than 2 μm. The textured surface is planarized by the intermediate layer or a layer of the perovskite photovoltaic cell. Forming the tandem photovoltaic device includes texturing a silicon containing layer of a silicon photovoltaic cell and operatively coupling a perovskite photovoltaic cell comprising a perovskite layer to the silicon photovoltaic cell, thereby forming a tandem photovoltaic device and planarizing the textured surface of the silicon containing layer of the silicon photovoltaic cell.

Disclosed is a solar cell including a semiconductor substrate, and a dopant layer disposed over one surface of the semiconductor substrate and having a crystalline structure different from that of the semiconductor substrate, the dopant layer including a dopant. The dopant layer includes a plurality of semiconductor layers stacked one above another in a thickness direction thereof, and an interface layer interposed therebetween. The interface layer is an oxide layer having a higher concentration of oxygen than that in each of the plurality of semiconductor layers.

Disclosed is a solar cell including a semiconductor substrate, and a dopant layer disposed over one surface of the semiconductor substrate and having a crystalline structure different from that of the semiconductor substrate, the dopant layer including a dopant. The dopant layer includes a plurality of semiconductor layers stacked one above another in a thickness direction thereof, and an interface layer interposed therebetween. The interface layer is an oxide layer having a higher concentration of oxygen than that in each of the plurality of semiconductor layers.

A solar battery according to the present embodiment has an electrode, which includes a metal and an adhesive material, formed in a conductive region including a polycrystalline semiconductor layer, and thus, the electrical characteristics of the solar battery may be improved and the manufacturing process thereof may be simplified. More specifically, the solar battery includes a semiconductor substrate, and the conductive region including the polycrystalline semiconductor layer is positioned on one surface of the semiconductor substrate.