Solar cell and solar cell module

A solar cell module comprising:

• a substrate;
• and
• first and second unit cells that are located on the substrate and that are connected in series to each other, each of the first and second unit cells including:
• a first electrode;
• a first hole transport layer containing nickel and lithium;
• an inorganic material layer containing titanium;
• a light-absorbing layer converting light into electric charge;
• a second hole transport layer, located between the first hole transport layer and the inorganic material layer, containing nickel and lithium;
• and
• a second electrode, wherein
• the first electrode, the first hole transport layer, the inorganic material layer, the light-absorbing layer, and the second electrode are layered on the substrate in that order,
• the light-absorbing layer contains a perovskite compound represented by a formula AMX3, where A is a monovalent cation, M is a divalent cation, and X is a monovalent anion,
• the first electrode, the first hole transport layer, and the inorganic material layer of the first unit cell are separated from the first electrode, the first hole transport layer, and the inorganic material layer of the second unit cell by a trench,
• the light-absorbing layer of the first unit cell is in contact with the first hole transport layer of the first unit cell and the first hole transport layer of the second unit cell in the trench, and
• an atomic ratio of lithium to all metal elements in the second hole transport layer is less than an atomic ratio of lithium to all metal elements in the first hole transport layer.

A solar cell comprising:

• a first electrode;
• a first hole transport layer containing nickel and lithium;
• an inorganic material layer containing titanium;
• a light-absorbing layer converting light into electric charge;
• a second hole transport layer, located between the first hole transport layer and the inorganic material layer, containing nickel and substantially no lithium;
• and
• a second electrode,
• wherein
• the first electrode, the first hole transport layer, the inorganic material layer, the light-absorbing layer, and the second electrode are layered in that order, and
• the light-absorbing layer contains a perovskite compound represented by a formula AMX3, where A is a monovalent cation, M is a divalent cation, and X is a monovalent anion.

A solar cell module comprising:

• a substrate;
• and
• first and second unit cells that are located on the substrate and that are connected in series to each other, each of the first and second unit cells including:
• a first electrode;
• a first hole transport layer containing nickel and lithium;
• an inorganic material layer containing titanium;
• a light-absorbing layer converting light into electric charge;
• a second hole transport layer, located between the first hole transport layer and the inorganic material layer, containing nickel and substantially no lithium;
• and
• a second electrode, wherein
• the first electrode, the first hole transport layer, the inorganic material layer, the light-absorbing layer, and the second electrode are layered on the substrate in that order;
• the light-absorbing layer contains a perovskite compound represented by a formula AMX3, where A is a monovalent cation, M is a divalent cation, and X is a monovalent anion;
• the first electrode, the first hole transport layer, and the inorganic material layer of the first unit cell are separated from the first electrode, the first hole transport layer, and the inorganic material layer of the second unit cell by a trench;
• and
• the light-absorbing layer of the first unit cell is in contact with the first hole transport layer of the first unit cell and the first hole transport layer of the second unit cell in the trench.