TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The first precursor is a source of B1, the second precursor is a source of A and X, where B1 is elements of group IVB, A is elements of group IA, and X is elements of group VIIB. The first precursor has a structure of formula (B1Y12), and the second precursor has a structure of formula (AX). The luminescent material has a structure of formula (AaB1bXx). The first precursor includes a first elemental precursor, the second precursor includes a second elemental precursor, and the luminescent material includes an alloy of the first elemental precursor and the second elemental precursor.B1 = Ge, Sn, or Pb;Y1, X = Cl, Br or I;A = K, Rb, Cs;a = 1;b = 1-5; andx = 1+2b.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The adhesive material includes a thermal-curable adhesive material, and applying the energy includes applying thermal energy. The adhesive material includes an UV-curable adhesive material, and applying the energy includes applying UV light. The luminescent layer is a first luminescent layer, the second assembly of layers further includes a second luminescent layer adjacent to the second reflector, and the second luminescent layer includes a third surface facing away from the second reflector. The luminescent stack further includes the second luminescent layer positioned between the bonding layer and the second reflector, and the bonding layer connects the first luminescent layer and the second luminescent layer. In the solar module, at least one of the first reflector and the second reflector includes a dielectric stack. The set of photovoltaic cells includes a first photovoltaic cell and a second photovoltaic cell, the first luminescent layer is configured to emit radiation corresponding to a first band gap energy of the first photovoltaic cell, and the second luminescent layer is configured to emit radiation corresponding to a second band gap energy of the second photovoltaic cell. Preferred Method: The step of providing the first assembly of layers includes forming the first reflector adjacent to the first substrate layer, and the step of providing the second assembly of layers includes forming the second reflector adjacent to the second substrate layer. In the method, at least one of forming the first reflector and forming the second reflector is carried out by atomic layer deposition of a set of dielectric materials. The step of bonding the first coating and the second coating is carried out by applying pressure and thermal energy to promote: inter-diffusion between the first coating and the second coating; and reaction between the first precursor and the second precursor to form the luminescent material. The step of providing the first assembly of layers includes forming the first coating adjacent to the first reflector by deposition of a first precursor of the luminescent material, and the step of providing the second assembly of layers includes forming the second coating adjacent to the second reflector by deposition of a second precursor of the luminescent material. The step of applying the adhesive material is such that the adhesive material is adjacent to at least one of the first surface of the first luminescent layer and the third surface of the second luminescent layer, and positioning the first assembly of layers and the second assembly layers is such that the adhesive material is between the first luminescent layer and the second luminescent layer.